CO2Rail aims to turn train cars into rolling carbon capture plants
We're seeing a growing emphasis on direct air capture technology in our efforts to combat climate change, and an interesting new take on this technology could see it put to use on railways around the world. US outfit CO2Rail is developing specialized rail cars that can be attached to existing trains and use energy from regenerative braking to power the onboard collection of carbon dioxide, preventing it from leaking into the atmosphere.
Direct air capture systems are gaining momentum as a potential weapon against climate change, by collecting CO2 from ambient air to negate its planet-warming potential. The US recently announced billions in new funding for research into this technology, and last month we also saw construction begin on what will become the world's largest direct air capture plant, which will soak up 36,000 tons of CO2 each year.
These types of facilities require land and tend to lean on renewable power sources such as solar or hydrothermal to power huge fans and filtering systems that capture the carbon. CO2Rail's idea is to have existing trains do the grunt work. Its purpose-built rail cars are designed to capture energy generated through regenerative braking to keep onboard batteries topped up, while leveraging the slipstream of the moving train in a "ramjet-type" process to avoid the need for fans.
This intake of air is directed into a large cylindrical CO2 collection chamber, where a chemical process separates the CO2 and stores it in a liquid reservoir to be emptied later. The clean, carbon-free air then flows harmlessly out of the back of the car and into the atmosphere. CO2Rail has now teamed up with scientists to crunch the numbers on its technology's potential, which are laid out in a newly published study.
According to the researchers, every complete train braking maneuver generates enough energy to power 20 homes for a day (currently, this energy is simply dissipated as a form of heat). If this was captured from nearly every stop made by every train around the world, it would amount to 105 times more energy than the Hoover Dam produces in the same timeframe. The figures put forward by the team on the carbon capture side of things are nothing to sneeze at either.
"This innovative technology will not only use the sustainable energy created by the braking maneuver to harvest significant quantities of CO2, but it will also take advantage of many synergies that integration within the global rail network would provide," explained study author Professor Peter Styring, from the University of Sheffield. “The technology will harvest meaningful quantities of CO2 at far lower costs and has the potential to reach annual productivity of 0.45 gigatons by 2030, 2.9 gigatons by 2050, and 7.8 gigatons by 2075 with each car having an annual capacity of 3,000 tonnes of CO2 in the near term.”
Achieving gigaton-scale removal of carbon dioxide is one of the key objectives of Climeworks, the company behind the world's largest direct air capture plant mentioned above. But equally important is the expense of doing so. Climeworks aims to drive its costs down to US$100 per ton of carbon removed, while Australian outfit Southern Green Gas is aiming for $72 a ton by harnessing the country's ample supply of solar. According to the new research, CO2Rail's technology has the potential to scale to a cost of $50 per ton.
“At these price points and with its tremendous capabilities, CO2Rail is likely to soon become the first megaton-scale, first gigaton-scale, and overall largest provider of direct air capture deployments in the world," said study author Professor Geoffrey Ozin from the University of Toronto.
The research was published in the journal Joule.
Source: University of Sheffield
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ref Braking Re-Gen Energy to Run Processing of Incoming Air:
On the assumption that the proposers have done their sums right - No comment.
ref 'while leveraging the slipstream of the moving train in a "ramjet-type" process to avoid the need for fans':
if the 'ramjet' is fed by direct funnel type collector forward facing then it will absorb energy from trains motive power feed.
If the ramjet inlet is fed by 'slipstream' then the collection set-up needs to be illustrated proper for comment
as one obvious prob' will be the creation of low pressure voids behind the kit wagon creating drag.
Ye Exceptions - The obvious freewheeling down hill runs, where these occur.
That said, it will, obviously, negate the energy recovered by the braking.
+ + +
Conclusion to Date:
Obviously . . ......
More definition needed.
Then the capture device - looks good in its green livery - I can see large railway companies employing them but not if they have to maintain and pay for them. Will there be a "Pullman System" to service the CO2 capture cars, switch them out and repair & recertify (or repair and replace components) as needed? And when 6m2 of 'slipstream' is eventually in process - how much will that increase the super-green rolling resistance?
There is no free lunch, but this concept is possible - at some cost and some infrastructure cost - most freight and passenger systems don't have that investment capacity - it appears it will be an environmental concern championed by governments or special interests.
The cars do indeed produce a drag force upon the train that consumes energy (~1,050 kWh/day for freight). However, since CO2Rail DAC cars do not require any air moving equipment during operation, there is a fairly substantial energy reduction per tonne of harvested CO2. This factor does greatly deminish the net energy consumption incurred from transportation of the car.
But again, the main advantage is capturing, storing, and utilizing the enormous regenerative braking energies that currently (in most areas) go completely wasted through rheostatic conversion (dynamic braking). This energy for all trains is estimated to be about 105x the output of the Hoover dam. We simply believe that this energy should be used for a productive purpose rather than wasted. No one could argue against that.
This, of course, then raises the question of what is the best use case for this energy. We have done derailed studies on the best use case for this otherwise wasted energy and, by far, utilizing it for on-board DAC mitigates the most carbon. When compared to using the energy for propulsion, only about 19% of CO2 emissions are mitigated as compared to using that same amount of energy for DAC operations.
Happy to answer more questions...